Air control mechanism



Aug. 18, 1936. T|N| EY 2,051,581

AIR CONTROL MECHANISM Filed Aug. 2, 1934 INVENTOR E12 8% 2d. 7k

ATTORNEY Patented Aug. 18, 1936 PATENT OFFICE j AIR CONTROL MECHANISM Ernest Lambert Tinley, Wolverhampton, England .Application August 2, 1934, Serial No. 738,165 In Great Britain May 16., .1934

3 Claims; (CI. 50-31) The inventionrelates toair control mechanism and :particularlyto mechanism adapted for'the regulation of the flow of a forced draught of air especially for usein connection with a mechanical stoker.

In most heating plants the capacity of most units'is designed for the peak load and for that reason it is necessary to be able to control the amount of airnot only according to the load due to the over-capacity of the units of the system, but also because of the varying conditions ofthe "fuel bed in ordinary combustion. Various attempts have been made to accomplish this objective, such as by thermal control.

In mechanical firing of heating plants it is particularly desirable for eificiency of operation that the correct quantity of air at the right pressure should be constantly supplied. Hence it is particularly desirable in the use of stokers that the control of the air supply should be sensitive and stable and not subject to hunting or oscillation.

The object of my invention is to provide means by which a sensitive and stable control of air or gas flowing in a duct is accomplished.

Another object of the invention is to provide a variable resistance to the flow of air or gas in a duct which is reduced with a rise and increased with a fall in the hydrostatic pressure beyond the variable resistance in the direction of the flow, and thereby maintain a constant rate of flow of the air.

The invention consists of a valve disposed in a duct and operatively responsive to changes in the resistance to the flow of air or gas in the duct at a point beyond the valve in the direction of said flow.

The invention is illustrated in the accompanying drawing in which Fig. 1 is a longitudinal cross-section of a mechanism embodying the invention. Fig. 2 is a transverse cross-section of a duct having the invention applied thereto and Fig. 3 is a fractional view in cross-section of a combustion chamber having the invention applied thereto.

Referring to the illustrative embodiment of the invention, I represents a section of a duct, leading, for example to the fire bed in a furnace and through which air is forced by a fan. A valve or damper 2 is pivotally mounted inthe duct I. A lever 3 is connected to the valve and a rod 4 is loosely pivoted to the lever and extends upwardly through a cylinder 5 that passes through an opening 6 in the duct I, is fixed in the bottom of the tank l3 and projects upwardly therefrom. The glands 1, 8 in the upper and lower ends of the cylinder seal the cylinder at said ends. .A Pitot tube 9 connects with the lower portion of the cylinder 5 and projects forwardly therefrom in the direction of flow of the air as indicated by the arrows in Fig. 1. The forward end of this -5 tube is perforated in its cylindrical surface and the circular end is enclosed.

A tank In is mounted on the duct. .A partition ll depends from the top I2 of the tank in spaced relation-to the side walls of the tank, its ,lower 10 edge being spaced from the bottom l3 of the tank. A wall 14 is fixed to the bottom .ofthe tank and forms a chamber 15 within ithaving communication at its upper end with the adjacent chamber l6. The ports [1 in the cylinder 15 form a communication between the cylinder and the chamber I5. The piston rod 4 is'connected at its upper end to a piston 3 that is in the form of an inverted cup, the depending wall of which is outside of. and spaced from the wall I4 of said chamber.

A casing l9 having a vent 20 therein is attached in an opening in the top l2 of the tank l0 so as to have communication with the chamber 2| formed between the wall of the tank 10 and the partition H. A valve 22 controls the vent 20 and regulates the rate of air flow through the vent into orfrom the chamber 2|.

.An opening 23 is formed in the toplZ through which a suitable quantity of liquid, preferably 39 oil, is supplied, the opening being normally closed by a plug 24. The liquid enters the'chamber 15 and rises in the chamber 2|, that in the chamber 16 forming an hydraulic seal for the piston.

The body of the damper 2 is attached to a bar 26, the opposite ends of which are engaged by the fulcrum screws 21 mounted in thebrackets 28 that are secured to the duct l. A counter weight 29 is carried by one'end of the bar 26, the said weight being adjustable on its supporting rod 30. The counterweight tends to swing the damper to wide open position and thereby cause the piston to rise to the upper limit of its movement. Any suitable manner of pivotally mounting the damper and connecting a counter-weight thereto will sufiice.

The static pressure in the duct I at the perforated end of the Pitot tube 9 is the measure of the resistance beyond the damper 2. This pressure is transferred by the tube to the chamber M where it reacts on the hydraulically sealed piston l1 causing it to rise or descend according to the rise or fall in the pressure at the forward end of the tube 9. The movements of the piston are transmitted by the rod 4 to the damper so that the damper is turned to increase or decrease the flow of air as the static pressure beyond it changes. Where the duct to be controlled supplies a draught of air to the fire bed of a furnace, the fuel for which is fed by a stoker, the resistance of the fire bed constitutes a variable resistance to the flow of air required for combustion.

When the pressure at the forward end of the tube 9 rises it reacts on the piston and the piston commences to rise and continues to do so until the pressure in the chamber 16 is equal to that in the chamber 15. The increased pressure depresses the level of the liquid in the chamber [6 and raises the level in the chamber 2|, the air in chamber 2| venting at the vent 28, the difference in levels corresponds to the pressure at the intake end of the tube 9. With a fall in pressure at said end of the tube the converse, of course, takes.

place. The piston is, therefore, in equilibrium in a definite position corresponding to any pressure at the intake end of tube 9 within the range for which the valve has been designed.

The upward movement of the piston, of course, opens the damper more or less and the reverse movement thereof closes the damper more or less. The damper, therefore, constitutes a variable resistance to the flow of air or gas in the duct and it is automatic in its operation. 7

In Fig. 3, I illustrate the application of the valve to the duct of a stoker mechanism in which the combustion chamber 3| is fed with fuel from a suitable stoker mechanism, not shown, a draught of air being supplied to the chamber through the duct I by a fan 32. The damper 2 is installed in the duct and connected to the piston [8 which floats in the tank H) as previously described. The

Pitot tube 9 extends toward the combustion chamber. As the resistance of the fire bed to the flow of air increases, the pressure in the duct increases, which is effective to raise the piston and open the damper and vice versa. Hence a constant flow of air is supplied in accordance with the resistance which the fuel bed offers to said flow.

What I claim is:

l. The combination with a duct for conveying air under pressure, of a damper in the duct, a plurality of chambers exteriorly of the duct, a piston connected to the damper and fluid sealed in one of the chambers, the latter chamber being closed to atmosphere above the piston, a conduit having communication with the piston-receiving chamber, and with the duct at points beyond the damper in the direction of the flow of the air and a vented chamber having communication with the lower portion of the piston-receiving chamber, the piston being responsive to changes in the resistance head in the duct beyond said damper.

2. The combination with a stoker fed combustion chamber and a duct for conveying air under pressure to the chamber; of a damper in the duct, a plurality of chambers one within another, a piston connected to the damper and fluid sealed in one of thechambers, said latter chamber being closed to atmosphere above the piston, a conduit having communication with the piston receiving chamber, and with the duct at points beyond the damper in the direction of flow of the air and another of said chambers having communication with the lower portion of the pistonreceiving chamber and having a controlled vent therein, the piston being responsive to changes in the resistance of the fire bed in the combustion chamber.

3. The combination with a stoker fed combustion chamber and a duct for conveying air under the pressure to the chamber, of a damper in the duct, a casing exteriorly of the duct, a wall dependingfrom the top of the casing toward the bottom thereof and forming an outer relatively narrow chamber adjacent to the side walls of the casing and a relatively larger chamber within the depending wall and communicating with the outer chamber, a vent in the casing for the outer chamber, a second wall extending upwardly from the bottom of the casing and spaced from the i;

first named wall and forming an inner chamber having communication with the upper portion of the relatively large chamber, a liquid seal in the outer chamber and in the portion of the relatively large chamber surrounding the second wall, a tube within the inner chamber and extending into the duct and having communication with said inner chamber, a piston connected to the damper and floating in the liquid seal and extending over the inner chamber and having its damper-connecting member extended through said tube, and a Pitot tube communicating with the inner chamber tube and with the duct at a point beyond the damper relatively to the direction of flow of the air therein.

ERNEST LAMBERT TINLEY. 

